To the Editor:—The article entitled "Chloroquine for Treatment of Acute Attacks of Vivax Malaria" by Most and his associates in the July 20 issue of The Journal brings up a point which has given us some concern.During the research period the investigators cooperating with the Board for the Coordination of Malarial Studies of the National Research Council were instructed by the board to calculate dosages of Aralen (Chloroquine) in terms of the amount of base contained, regardless of the salt used. This was entirely logical, since the investigators were engaged in comparative studies on a large number of compounds and their chief concern was to obtain information on the active principles of the drugs involved.When the compounds were carried over into clinical research this practice was continued, and in the case of Aralen, although the diphosphate was used, dosages continued to be expressed in terms of the